Switchgrass Biomass and Nitrogen Yield with Over-Seeded Cool-season Forages in the Southern Great Plains
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Switchgrass Biomass and Nitrogen Yield with Over-Seeded Cool-season Forages in the Southern Great Plains Twain J. Butler & James P. Muir & Chengjun Huo & John A. Guretzky
Published online: 17 June 2012 # Springer Science+Business Media, LLC 2012
Abstract In dry climates with long, hot summers and freezing winters, such as that of the southern Great Plains of North America, switchgrass (Panicum virgatum L.) has proven potential as a cellulosic bioenergy feedstock. This trial looked at dry matter (DM) and N yield dynamics of switchgrass overseeded with cool-season legumes and rye (Secale cereale L.), compared to switchgrass fertilized with 0, 56 and 112 kg N ha-1 yr-1 at an infertile and a fertile location. Optimal N fertilizer rate on switchgrass was 56 kg N ha-1 at the infertile location. Legume yield was greater in the first season after planting, compared to subsequent years where annual legumes were allowed to reseed and alfalfa (Medicago sativa L.) was allowed to grow. This suggests that the reseeding model for annual legumes will not work in switchgrass swards grown for biomass unless soil seed banks are built up for more than one year, and that overseeding with alfalfa may have to be repeated in subsequent years to build up plant populations. Overseeding rye and legumes generally did not suppress or enhance switchgrass biomass production compared to unfertilized switchgrass. However, cumulative spring and fall biomass yields were generally greater due to winter and spring T. J. Butler : C. Huo The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA J. P. Muir (*) Texas AgriLife Research, Texas A&M System, 1229 N. HWY 281, Stephenville, TX 76401, USA e-mail: [email protected] J. A. Guretzky Department of Agronomy and Horticulture, University of Nebraska-Lincoln, 310 Keim Hall, Lincoln, NE 68583-0915, USA
legume production, which could be beneficial for grazing or soil conservation systems, but not necessarily for once-yearly late autumn harvest biofuel production systems. Keywords Switchgrass biomass yield . Nitrogen yield . Cool-season legumes . Clover . Hairy vetch . Medics . Rye Abbreviations DM dry matter OM organic matter
Introduction Extensive research in the southern Great Plains of North America has identified switchgrass as a productive and widely adapted cellulosic bioenergy feedstock [1]. In the dry, variable rainfall climates of this region, where temperatures often fall below 0 °C in the winter but regularly rise above 45 °C in the summer, switchgrass, a perennial grass native to North America, tolerates low soil fertility, responds to low levels of N fertilizer, and persists under single harvest cultivation once established [1–3]. Although precipitation amounts and distribution vary widely from year to year in this semiarid region, with consequent variable switchgrass DM yields [3, 4], this deep-rooted bunchgrass has the potential to provide cellulosic bioenergy feedstock in a region that is poorly adapted to annual dryland cropping systems. Most of what we know about
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